/*
       Copyright (c) 2000 The Legion Of The Bouncy Castle
       (http://www.bouncycastle.org)
       
       Permission is hereby granted, free of charge, to any person obtaining
       a copy of this software and associated documentation files (the "Software"),
       to deal in the Software without restriction, including without limitation
       the rights to use, copy, modify, merge, publish, distribute, sublicense,
       and/or sell copies of the Software, and to permit persons to whom the Software
      is furnished to do so, subject to the following conditions:
      
      The above copyright notice and this permission notice shall be included in all
      copies or substantial portions of the Software. 
      
      THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
      IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
      FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
      AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
      LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
      OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN 
      THE SOFTWARE. 
      */
      package org.bouncycastle.util.encoders;
      
      public class Base64
      {
      		private static final byte[] encodingTable =
	      		{
	      		    (byte)'A', (byte)'B', (byte)'C', (byte)'D', (byte)'E', (byte)'F', (byte)'G',
	                  (byte)'H', (byte)'I', (byte)'J', (byte)'K', (byte)'L', (byte)'M', (byte)'N',
	                  (byte)'O', (byte)'P', (byte)'Q', (byte)'R', (byte)'S', (byte)'T', (byte)'U',
	                  (byte)'V', (byte)'W', (byte)'X', (byte)'Y', (byte)'Z',
	      		    (byte)'a', (byte)'b', (byte)'c', (byte)'d', (byte)'e', (byte)'f', (byte)'g',
	                  (byte)'h', (byte)'i', (byte)'j', (byte)'k', (byte)'l', (byte)'m', (byte)'n',
	                  (byte)'o', (byte)'p', (byte)'q', (byte)'r', (byte)'s', (byte)'t', (byte)'u',
	                  (byte)'v',(byte)'w', (byte)'x', (byte)'y', (byte)'z',
	      		    (byte)'0', (byte)'1', (byte)'2', (byte)'3', (byte)'4', (byte)'5', (byte)'6',
	                  (byte)'7', (byte)'8', (byte)'9',
	      		    (byte)'+', (byte)'/'
	      		};
      
      	/**
      	 * encode the input data producong a base 64 encoded byte array.
      	 *
      	 * @return a byte array containing the base 64 encoded data.
      	 */
      	public static byte[] encode(byte[]	data)
      	{
      		byte[]	bytes;
      		
      		int modulus = data.length % 3;
      		if (modulus == 0)
      		{
      			bytes = new byte[4 * data.length / 3];
      		}
      		else
      		{
      			bytes = new byte[4 * ((data.length / 3) + 1)];
      		}
      
              int dataLength = (data.length - modulus);
      		int a1, a2, a3;
      		for (int i = 0, j = 0; i < dataLength; i += 3, j += 4)
      		{
      			a1 = data[i] & 0xff;
      			a2 = data[i + 1] & 0xff;
      			a3 = data[i + 2] & 0xff;
      
      			bytes[j] = encodingTable[(a1 >>> 2) & 0x3f];
      			bytes[j + 1] = encodingTable[((a1 << 4) | (a2 >>> 4)) & 0x3f];
      			bytes[j + 2] = encodingTable[((a2 << 2) | (a3 >>> 6)) & 0x3f];
      			bytes[j + 3] = encodingTable[a3 & 0x3f];
      		}
      
      		/*
      		 * process the tail end.
      		 */
      		int	b1, b2, b3;
      		int	d1, d2;
      
      		switch (modulus)
      		{
	      		case 0:		/* nothing left to do */
	      			break;
	      		case 1:
	      			d1 = data[data.length - 1] & 0xff;
	      			b1 = (d1 >>> 2) & 0x3f;
	      			b2 = (d1 << 4) & 0x3f;
	      
	      			bytes[bytes.length - 4] = encodingTable[b1];
	      			bytes[bytes.length - 3] = encodingTable[b2];
	      			bytes[bytes.length - 2] = (byte)'=';
	      			bytes[bytes.length - 1] = (byte)'=';
	      			break;
	      		case 2:
	      			d1 = data[data.length - 2] & 0xff;
	      			d2 = data[data.length - 1] & 0xff;
	     
	     			b1 = (d1 >>> 2) & 0x3f;
	     			b2 = ((d1 << 4) | (d2 >>> 4)) & 0x3f;
	     			b3 = (d2 << 2) & 0x3f;
	     
	     			bytes[bytes.length - 4] = encodingTable[b1];
	     			bytes[bytes.length - 3] = encodingTable[b2];
	     			bytes[bytes.length - 2] = encodingTable[b3];
	     			bytes[bytes.length - 1] = (byte)'=';
	     			break;
     		}
     
     		return bytes;
     	}
     
     	/*
     	 * set up the decoding table.
     	 */
     	private static final byte[] decodingTable;
     
     	static
     	{
     		decodingTable = new byte[128];
     
     		for (int i = 'A'; i <= 'Z'; i++)
     		{
     			decodingTable[i] = (byte)(i - 'A');
     		}
     
     		for (int i = 'a'; i <= 'z'; i++)
     		{
     			decodingTable[i] = (byte)(i - 'a' + 26);
     		}
     
     		for (int i = '0'; i <= '9'; i++)
     		{
     			decodingTable[i] = (byte)(i - '0' + 52);
     		}
     
     		decodingTable['+'] = 62;
     		decodingTable['/'] = 63;
     	}
     
     	/**
     	 * decode the base 64 encoded input data.
     	 *
     	 * @return a byte array representing the decoded data.
     	 */
     	public static byte[] decode(byte[]	data)
     	{
     		byte[]	bytes;
     		byte	b1, b2, b3, b4;
     
     		if (data[data.length - 2] == '=')
     		{
     			bytes = new byte[(((data.length / 4) - 1) * 3) + 1];
     		}
     		else if (data[data.length - 1] == '=')
     		{
     			bytes = new byte[(((data.length / 4) - 1) * 3) + 2];
     		}
     		else
     		{
     			bytes = new byte[((data.length / 4) * 3)];
     		}
     
     		for (int i = 0, j = 0; i < data.length - 4; i += 4, j += 3)
     		{
     			b1 = decodingTable[data[i]];
     			b2 = decodingTable[data[i + 1]];
     			b3 = decodingTable[data[i + 2]];
     			b4 = decodingTable[data[i + 3]];
     
     			bytes[j] = (byte)((b1 << 2) | (b2 >> 4));
     			bytes[j + 1] = (byte)((b2 << 4) | (b3 >> 2));
     			bytes[j + 2] = (byte)((b3 << 6) | b4);
     		}
     
     		if (data[data.length - 2] == '=')
     		{
     			b1 = decodingTable[data[data.length - 4]];
     			b2 = decodingTable[data[data.length - 3]];
     
     			bytes[bytes.length - 1] = (byte)((b1 << 2) | (b2 >> 4));
     		}
     		else if (data[data.length - 1] == '=')
     		{
     			b1 = decodingTable[data[data.length - 4]];
     			b2 = decodingTable[data[data.length - 3]];
     			b3 = decodingTable[data[data.length - 2]];
     
     			bytes[bytes.length - 2] = (byte)((b1 << 2) | (b2 >> 4));
     			bytes[bytes.length - 1] = (byte)((b2 << 4) | (b3 >> 2));
     		}
     		else
     		{
     			b1 = decodingTable[data[data.length - 4]];
     			b2 = decodingTable[data[data.length - 3]];
     			b3 = decodingTable[data[data.length - 2]];
     			b4 = decodingTable[data[data.length - 1]];
     
     			bytes[bytes.length - 3] = (byte)((b1 << 2) | (b2 >> 4));
     			bytes[bytes.length - 2] = (byte)((b2 << 4) | (b3 >> 2));
     			bytes[bytes.length - 1] = (byte)((b3 << 6) | b4);
     		}
     
     		return bytes;
     	}
     
     	/**
     	 * decode the base 64 encoded String data.
     	 *
     	 * @return a byte array representing the decoded data.
     	 */
     	public static byte[] decode(String	data)
     	{
     		byte[]	bytes;
     		byte	b1, b2, b3, b4;
     
     		if (data.charAt(data.length() - 2) == '=')
     		{
     			bytes = new byte[(((data.length() / 4) - 1) * 3) + 1];
     		}
     		else if (data.charAt(data.length() - 1) == '=')
     		{
     			bytes = new byte[(((data.length() / 4) - 1) * 3) + 2];
    		}
     		else
     		{
     			bytes = new byte[((data.length() / 4) * 3)];
     		}
     
     		for (int i = 0, j = 0; i < data.length() - 4; i += 4, j += 3)
     		{
     			b1 = decodingTable[data.charAt(i)];
     			b2 = decodingTable[data.charAt(i + 1)];
     			b3 = decodingTable[data.charAt(i + 2)];
     			b4 = decodingTable[data.charAt(i + 3)];
     
     			bytes[j] = (byte)((b1 << 2) | (b2 >> 4));
     			bytes[j + 1] = (byte)((b2 << 4) | (b3 >> 2));
     			bytes[j + 2] = (byte)((b3 << 6) | b4);
     		}
     
     		if (data.charAt(data.length() - 2) == '=')
    		{
     			b1 = decodingTable[data.charAt(data.length() - 4)];
     			b2 = decodingTable[data.charAt(data.length() - 3)];
     
     			bytes[bytes.length - 1] = (byte)((b1 << 2) | (b2 >> 4));
     		}
     		else if (data.charAt(data.length() - 1) == '=')
     		{
     			b1 = decodingTable[data.charAt(data.length() - 4)];
     			b2 = decodingTable[data.charAt(data.length() - 3)];
     			b3 = decodingTable[data.charAt(data.length() - 2)];
     
     			bytes[bytes.length - 2] = (byte)((b1 << 2) | (b2 >> 4));
     			bytes[bytes.length - 1] = (byte)((b2 << 4) | (b3 >> 2));
     		}
     		else
     		{
     			b1 = decodingTable[data.charAt(data.length() - 4)];
     			b2 = decodingTable[data.charAt(data.length() - 3)];
     			b3 = decodingTable[data.charAt(data.length() - 2)];
     			b4 = decodingTable[data.charAt(data.length() - 1)];
     
     			bytes[bytes.length - 3] = (byte)((b1 << 2) | (b2 >> 4));
     			bytes[bytes.length - 2] = (byte)((b2 << 4) | (b3 >> 2));
     			bytes[bytes.length - 1] = (byte)((b3 << 6) | b4);
     		}
     
     		return bytes;
     	}
     }